1. Field of the Invention
The present invention relates generally to the field of cellular foams and the method of making the same, and, more specifically, to a cellular foam having anti-fogging characteristics.
2. Description of the Prior Art
In the automotive industry, a recognized problem has been the formation of volatile condensate or xe2x80x9cfogxe2x80x9d on the interior and windshield of the automobile. This residue is unsightly, and may impair the vision of the driver under certain circumstances. One source of the fogging is believed to be the flexible foam gaskets which are in place to seal the interior to exterior passageways of the automobile, such as the door, tail lights, windows, etc. When these gaskets are exposed to thermal cycling during the life of the automobile, the gaskets tend to emit volatile compounds into the interior environment of the vehicle. The volatile compounds eventually condense on the windshield and other surfaces inside the vehicle, forming the xe2x80x9cfog.xe2x80x9d Over time, emission of the volatile compounds also will degrade the gasket to the point where it will no longer perform its intended function properly.
In response to the fogging problem, the Society of Automotive Engineers (xe2x80x9cSAExe2x80x9d) has developed a standard test to quantify the fogging characteristics of materials used in automotive interiors, which it issued December 1994 and has designated as SAE standard J1756. SAE standard J1756 is well known in the art, and is incorporated herein by reference. Similar standards have been established by Ford Motor Corporation, General Motors Corporation, and other automotive component manufacturers.
At present, the only foam seals known to achieve acceptable results on the SAE J1756 test have been barrier or film coated to effectively block or close the surface of the foam and thereby prohibit or reduce emission of volatiles from the foam. Although such foams satisfy the SAE J1756 test, it is desired to provide a foam which is not barrier or film coated, but which inherently has the same or similar properties and which will achieve acceptable results on these tests. One advantage to such an anti-fogging foam would be in the reduction of manufacturing costs. Foam which must be barrier or film coated is generally more costly to manufacture as additional or more expensive components are required to make such a foam, and the additional processing required to apply the barrier or film coating adds cost as well.
Another advantage of an anti-fogging foam which is not barrier or film coated would be in the enhanced conformability of the foam. Conformability is desired because, to effectively seal the interior to exterior passageways of the automobile, the foams must be adapted to fit the sometimes tight radii and intricate contours of these passageways. Barrier or film coated foam is less conformable than anti-fogging foams which do not require barrier or film coating. A more conformable foam will provide a better seal, for a longer period of time, than a less conformable foam.
It should be noted that the xe2x80x9cfoggingxe2x80x9d problem is not unique to the automotive industry. Anti-fogging foam gaskets have applications in other areas where dirt and condensate residue would have a deleterious effect. Such applications would include, for example, electronics or semiconductor manufacturing facilities, electronics packaging, clean rooms, and medical device applications.
The present invention comprises a cellular foam composition, and method for making the same. In one embodiment, the foam comprises a mixture of glutarate ester plasticizer, adipate ester plasticizer, alcohol carboxylic acid ester, cell stabilizer, barium/zinc activator stabilizer, potassium/zinc activator stabilizer, azodicarbonamide blowing agent, low-fogging vinyl dispersion resin, vinyl blending resin, and black acrylic pigment dispersion. In another embodiment, the foam comprises a mixture of glutarate ester plasticizer, adipate ester plasticizer, alcohol carboxylic acid ester, cell stabilizer, barium/zinc activator stabilizer, zinc stabilizer, azodicarbonamide blowing agent, low-fogging vinyl dispersion resin, vinyl blending resin, and black acrylic pigment dispersion.
The foam is made by the process of mixing the ingredients until a homogenous liquid mixture is present, de-airing the homogeneous liquid mixture, casting the liquid mixture on a non-fogging release-coated surface, expanding the cast liquid mixture by exposing it to an elevated temperature for a prescribed duration of time, and then either cooling the expanded mixture and winding it into rolls, or coating the stabilized composition with pressure sensitive adhesive, cooling it, and then winding it into rolls. The resulting low volatility foam is reasonable in cost of its components and in cost of manufacture, and exhibits anti-fogging characteristics desired in a variety of applications. These results are accomplished without requiring barrier or film coating of the foam.